The present invention relates to the transmission of data and, in particular, to data sets.
Workers in the data transmission art, particularly in the area of voiceband data transmission, have suggested various data set, or modem, designs which, in some way, operate under programmed processor, e.g., microprocessor, control. Such designs are disclosed, for example, in K. I. Nordling et al, Proceedings 1976 National Telecommunications Conference, p. 50.2.1 et seq; K. Watanabe et al, Conference Record, 1977 International Conference on Communications, p. 47.6-252 et seq; P. J. Van Gerwin et al, IEEE Trans. on Comm., February 1977, p. 238 et seq; U.S. Pat. No. 4,085,449 issued Apr. 18, 1978 to D. M. Walsh et al.
One advantage of incorporating a programmed processor into a data set is that the design of the data set can be updated relatively inexpensively via program modification both during development of the design and after full-scale manufacturing has begun. Another advantage is that the data set can, with relative ease, be designed to operate with, for example, a number of signaling rates and modulation formats. Moreover, incorporating a programmed processor into the design makes it economically feasible to provide the data set with sophisticated features, particularly in the area of data set and network diagnostics.
In a number of prior art designs, the real-time signal processing of user-provided data and received data signals is performed under program control by the processor itself. In order to ensure that all the processing which needs to be done within one symbol interval can be completed, these designs typically utilize so-called bit-slice processors, at least for high-bit-rate (4800 bit per second or greater) data sets. A drawback of this approach is that bit-slice processors must be custom-designed by the data set designer. This adds to the complexity of the design task. Moreover, it requires expertise in such areas as computer processor architecture and hardware--areas with which the person skilled in the data transmission art may not be familiar.
It may be possible to design a data set which is able to perform the necessary processing using a conventional, e.g., MOS, processor. A drawback, however, is that substantial programming effort must be devoted in such a design to keeping real-time transmit and receive functions from interfering with one another. Another drawback is that no matter whether a conventional or bit-slice processor is used, the processing capability of the processor may be substantially consumed with real-time signal processing tasks, leaving little, if any, processor capability for diagnostics or other functions. A potential way to deal with these drawbacks is to divide the data set functions between two or more processors. There may be difficulty, however, in coordinating their operations.